Intramuscular administration of 5 alpha-dihydrotestosterone heptanoate: changes in urinary hormone profile.

A recommended confirmatory procedure for detecting 5 alpha-dihydrotestosterone (DHT) doping in male athletes proposed the use of the urinary concentration ratio of DHT to epitestosterone (EpiT) as the primary marker and those of 5 alpha-androstane-3 alpha,17 beta-diol (5 alpha-Adiol) to EpiT, luteinizing hormone (LH), and 5 beta-androstane-3 alpha,17 beta-diol (5 beta-Adiol) as secondary markers. Here we investigate the effects on these markers of intramuscular administration of DHT heptanoate (250 mg) to six healthy men. Within 24 h of administration all four markers greatly exceeded the published discrimination limits, remaining above these limits for 10-14 days. All ratios returned to basal values by day 28. In contrast to results after percutaneous administration, 5 beta-Adiol excretion decreased, probably as a consequence of greater suppression of testicular steroidogenesis. Results were largely in agreement with those obtained after percutaneous administration, although probably augmented by the larger dose and the different route of delivery.

Inhibition of uricase by pyrimidine and purine drugs.

A number of barbiturates inhibit uricase from porcine liver competitively, the Ki, values being in the range 1 to 13 X 10(-3) mol/L. In general the Ki increases as the size of the substituents at C-5 increases. Theophylline also inhibits the enzyme competitively (Ki = 1 X 10(-3) mol/L) but theobromine and caffeine have no inhibitory action at 0.01 mol/L. A number of sulphonamides and some other heterocyclic compounds, at 10(-3) mol/L, do not inhibit uricase. The possible effects of such inhibition in clinical assays for plasma/serum urate are discussed but it is concluded that the compounds which were studied are unlikely to cause significant interference in the assay.